Isobutene is commercially significant in many applications. For example, isobutene is one of the comonomers in butyl rubber. Isobutene can also be oligomerized to produce compounds that can be used as chemical feedstock for further reacting or in gasoline blending. Diisobutene, the isobutene dimer, is of particular commercial value in several applications. For example, diisobutene can be used as an alkylation reaction feedstock or as an intermediate in the preparation of detergents. Diisobutene can also be hydrogenated to pure isooctane (2,2,4-tri-methyl pentane) that is highly preferred in gasoline blending.
Isoolefin oligomerization is a catalytic reaction that may be performed using an acid resin catalyst. For example, oligomerization of isoolefins has been disclosed in U.S. Pat. Nos. 4,242,530, 4,375,576, 5,003,124, and 7,145,049, 6,335,473, 6,774,275, 6,858,770, 6,936,742, 6,995,296, 7,250,542, 7,288,693, 7,319,180, 6,689,927, 6,376,731, 5,877,372, 4,331,824, 4,100,220 and U.S. Patent Application Publication Nos. 20080064911, 20080045763, 20070161843, 20060030741, 20040210093, and 20040006252, among others. Acid resin catalysts have also found use in various other petrochemical processes, including formation of ethers, hydration of olefins, esterifications, and expoxidations, such as described in U.S. Pat. Nos. 4,551,567 and 4,629,710.
Processes for oligomerization of olefins over such resin catalysts require periodic shutdowns of the oligomerization unit to replace and/or regenerate the catalysts. Further, such solid-catalyzed processes may require additives (“selectivators”) to promote the selectivity of the catalyst to the dimer, where the additives may result in unwanted acid throw, deactivating the catalyst, and may additionally require complicated separation processes to remove the additive from the resulting product streams.
Accordingly, there exists a continuing need for improved isoolefin dimerization catalysts and processes.